In the electrophilic aromatic substitution of pyrrole at the kinetically preferred C-2 position, how many valid resonance structures (canonical forms) can be drawn to delocalize the positive charge in

Question

In the electrophilic aromatic substitution of pyrrole at the kinetically preferred C-2 position, how many valid resonance structures (canonical forms) can be drawn to delocalize the positive charge in the intermediate arenium ion?

Prashant Kotian · Accepted Answer

Correct answer: 3. When an electrophile attacks pyrrole at the C-2 position, the resulting positive charge can be delocalized across the adjacent carbon atoms and onto the nitrogen atom via its lone pair. This results in exactly 3 distinct resonance structures, compared to only 2 structures for attack at the C-3 position. The most stable of these 3 structures places the positive charge on the nitrogen atom, granting every atom a complete octet.

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